Thanks for the tips.

The .exe was compiled with VFP 6 SP2 or later - I'm not sure if it used SP3.
I also tried ensuring that DCOM was installed on all the PC's, as I heard this can solve the C05 problem - to no avail. I will explore the possibility of a bad network card, though no other VFP/FOX DOS apps they are running have corruption problems.

Thanks again.